Recently, silicon nanocrystals have been widely used as photoelectric conversion/photo conversion materials used in, for example, solar cells or light emitting devices (LEDs). Of various methods for preparing silicon nanoparticles, a vapor state reaction is advantageous for grain size control of highly pure silicon nanoparticles and utilizes mainly laser or thermal plasma. With such an energy source, however, the silicon nanoparticles are apt to aggregate, due to high calorific heat, into secondary particles having a size of several micrometers (μm).
As a solution to such problems, low-temperature plasma such as inductively coupled plasma (ICP) has recently been used to prevent the aggregation of silicon nanocrystals.
A conventional ICP-based apparatus for producing silicon nanoparticles has a structure in which a reactor is wound with an ICP coil around the outer circumference thereof and is simultaneously supplied with a first gas for the formation of silicon nanoparticles and a second gas for the surface reaction of silicon nanoparticles.
For such a conventional ICP-based apparatus, however, a wide plasma reaction area is caused by plasma diffusion inside the reactor, resulting in making it difficult to control the grain size of the silicon nanoparticles. The plasma diffusion also causes a wide reaction area of the second gas, and extends reaction time, thereby making it difficult to control the grain size of silicon nanoparticles and lowering the production yield.
Therefore, there is a need for an apparatus for producing silicon nanoparticles using ICP (Inductive Coupled Plasma) that can facilitate the control of the grain size of silicon nanoparticles by making the plasma reaction uniform across the inside of the reactor and that can increase the production yield through the maximization of reaction efficiency by forming a high density of plasma.